Add Style struct

[mrichards42]

Based on #50 and #51 this adds a Style struct to all widgets.

I've left in the concept of defaults, but instead of those being individual static members of the style class (DEFAULT_FS, DEFAULT_JUSTIFY), there's now a default Style, so anything in the Style struct can have a default.

The style system involves three classes:

• Style -- a simple struct holding all style information.
• Stylesheet -- used to update individual parts of a Style.
• Stylesheet::Inherited -- a Stylesheet used to copy some variables from one Style to another.

The approach this PR suggests to managing styles is to create a Stylesheet and apply it to widgets as appropriate. Some widgets have default stylesheets (e.g. Button). For instance, suppose you have two different kinds of buttons you might want to support in your app. One with an outline and centered text, and the other with an underline and left-aligned text. This might look like:

// Although note valign and border are not implemented yet.
Stylesheet OUTLINED_BUTTON_STYLE = Stylesheet().border(1).valign_middle().justify_center();
Stylesheet UNDERLINED_BUTTON_STYLE = Stylesheet().underline(true).valign_top().justify_left();

auto btnA = new ui::Button(...);
btnA->set_style(OUTLINED_BUTTON_STYLE);

auto btnB = new ui::Button(...);
btnB->set_style(UNDERLINED_BUTTON_STYLE);

Alternate approaches

I started going down the road of creating a separate style hierarchy that would be used via multiple inheritance. That's a little more flexible, but less straightforward and IMO a little more confusing (as things always are w/ multiple inheritance). The advantage is mostly that you don't have to store every style in every class, since not all styles will be relevant in every class. There's probably a way to get something similar using has-a instead of is-a, but the solution wasn't immediately obvious to me. An example:

struct StyleBase {
  virtual ~StyleBase() {} // needs to be polymorphic for Stylesheet to work
};

struct TextStyle : StyleBase {
  int font_size;
  bool underline;
}

struct AlignStyle : StyleBase {
  enum JUSTIFY { ... }
  enum VALIGN { ... }
  JUSTIFY justify;
  VALIGN valign;
}

class Text : public Widget, public TextStyle, public AlignStyle {
  ...
}

auto text = new ui::Text(...);
Stylesheet().font_size(32).justify_center().apply(text);

[mrichards42]

Replaced by set_style()

[raisjn]

this is super cool, code looks great - i'll compile and test things out

[raisjn]

if only there was easier metaprogramming :-(

[mrichards42]

I mean, there's always macros :)

[raisjn]

most things compile (remux, harmony, mines, sharenote, simple, etc) except for minesweeper:

diff --git a/src/minesweeper/main.cpy b/src/minesweeper/main.cpy
index d31a93b..f7855e4 100644
--- a/src/minesweeper/main.cpy
+++ b/src/minesweeper/main.cpy
@@ -37,7 +37,7 @@ void main_menu()
 void resize_field(int)
 void show_scores()
 
-ui::Style LARGE_TEXT = Stylesheet().font_size(64)
+ui::Style LARGE_TEXT = ui::Stylesheet().font_size(64).build()
 
 class SizeButton: public ui::Button:
   public:
@@ -391,7 +391,7 @@ class App:
     button_height := 200
     for auto p : sizes:
       btn := new SizeButton(w/2-400, 500, 800, button_height, p.first, p.second)
-      btn->y_padding = (button_height - btn.style.font_size) / 2
+      btn->y_padding = (button_height - btn->style.font_size) / 2
       size_button_container.pack_start(btn)
       debug "BTN", btn->x, btn->y
 
@@ -401,7 +401,7 @@ class App:
 //    size_button_container.pack_start(new SizeButton(w/2-400, 50, 800, 200, 20, "20x20"))
 
     scores := new ScoresButton(w/2-400, 500, 800, button_height)
-    scores->y_padding = (button_height - btn.style.font_size) / 2
+    scores->y_padding = (button_height - scores->style.font_size) / 2
     debug scores->x, scores->y
     size_button_container.pack_start(scores)
     debug scores->x, scores->y

but this made me think that you maybe had plans for valign (which would make these lines obsolete).

i also tested out remux, harmony, mines, simple - everything looks good so far

[mrichards42]

Woops -- sorry I was doing test compiles along the way, but that diff was a last-minute change and I must not have tried to compile it.

Yep, I was thinking about having valign be the next PR.

i also tested out remux, harmony, mines, simple - everything looks good so far

Awesome, thanks for testing those. I think I made changes in the right places, but I don't know enough about the rest of the apps to know if something was broken visually.

[mrichards42]

Latest commits should address c++17 syntax, the failed minesweeper build, and operator+=

LMK if you'd prefer rebasing those into the previous commits instead of adding new ones.

[mrichards42]

There were a couple files where it looked like okp wasn't adding the semicolon after the last class. Maybe when there are multiple classes in the file?

[raisjn]

      self.textWidget->set_style(Stylesheet::Inherited(self.style).text_style())

vs

      self.textWidget->set_style(self.style.inherit().text_style())

[raisjn]

thank you for the diff!